Molecular mechanisms involved in the antiproliferative effect of two COX-2 inhibitors, nimesulide and NS-398, on colorectal cancer cell lines

BACKGROUND

Cyclooxygenase (COX)-2 is up-regulated in most colorectal cancers. Chronic use of non-steroidal anti-inflammatory drugs, which target cyclooxygenases, have been shown to reduce the risk of these cancers. However, the mechanisms underlying this protective effect remain unclear.

AIMS

The aim of our study was to characterize the effects of two COX-2 selective inhibitors, NS-398 and nimesulide, on colorectal cancer cell proliferation, and to describe the molecular mechanisms involved.

MATERIALS AND METHODS

HT-29 and SW-1116 cell lines were cultured with either NS-398 or nimesulide. Cell proliferation was assessed by staining DNA with crystal violet. Cell cycle repartition and apoptosis were analysed by flow cytometry. The expression of COX-1 and COX-2. and of two cyclin dependent kinase inhibitors, p21Cip1 and p27Kip1, was analysed by Western blotting and RT-PCR.

RESULTS

Both drugs dose-dependently inhibited cell proliferation and induced G1 cell cycle blockade. HT-29 cells were more sensitive to both drugs than SW-1116 cells. p21Cip1 and p27Kip1 were induced on both cell lines. Concomitant induction of p21Cip1 mRNA indicates transcriptional modulation, whereas induction of p27Kip1 only at the protein level suggests post-translational modulation.

CONCLUSION

NS-398 and nimesulide inhibit colorectal cell proliferation through induction of p21Cip1 and p27Kip1.

RDP58, a novel immunomodulatory peptide with anti-inflammatory effects. A pharmacological study in trinitrobenzene sulphonic acid colitis and Crohn disease

BACKGROUND

Tumour necrosis factor (TNF) plays a key role in the pathogenesis of Crohn disease (CD). RDP58 is a novel anti-inflammatory decapeptide which was developed using a novel rational design strategy. Recently, RDP58 has proved to be a potent inhibitor of TNF production at a post-transcriptional step. The aims of this study were to investigate the anti-inflammatory properties of RDP58 ex vivo in human CD and in vivo in an experimental model colitis.

METHODS

Biopsies and lamina propria mononuclear cells from inflamed colonic mucosa of 18 CD patients were cultured for 24 h in the presence or absence of RDP58. TNF was quantified in a bioassay: interferon (IFN)-gamma and interleukin (IL)-1beta levels were measured by enzyme-linked immunosorbent assays. Colitis was induced by intra-rectal administration of 2, 4, 6 trinitrobenzene sulphonic acid (TNBS) in rats. Inflammation was assessed following 7 days of oral therapy with RDP58 or vehicle alone.

RESULTS

RDP58 led to decreased TNF and IFN-gamma (but not IL-1beta) production by biopsies and lamina propria mononuclear cells from CD patients. In rats with TNBS-induced colitis, oral RDP58 therapy reduced weight loss and diarrhoea and improved macroscopic and histological inflammation scores.

CONCLUSIONS

Our results suggest that RDP58 may be an effective therapy for CD with the clinical advantage of an oral administration.

Changes in chemical coding of myenteric neurones in ulcerative colitis

BACKGROUND

Morphological and functional changes in the enteric nervous system (ENS) have been reported in inflammatory bowel diseases but it is still uncertain whether neurochemical coding of myenteric neurones is altered in ulcerative colitis (UC).

AIMS

In this study we investigated transmitter co-localisation in myenteric neurones of normal colon and the colon of patients with UC.

METHODS

Choline acetyltransferase (ChAT), neurone specific enolase (NSE), vasoactive intestinal peptide (VIP), and substance P (SP) were detected by immunohistochemical methods in whole mounts of colonic myenteric plexus of UC patients (n=10) and controls (n=8).

RESULTS

The proportion of ChAT positive and VIP positive neurones relative to the NSE population did not differ in inflamed (33.3% and 9.3%, respectively) and non-inflamed segments (33.6% and 9.7%) of UC colon compared with controls (35.0% and 6.9%). The proportion of SP positive neurones was significantly larger in both inflamed (15.5%) and non-inflamed (20.3%) segments than in controls (5.9%). Analysis of changes in subpopulations showed that 26.9% of neurones were only ChAT positive in controls but that the proportion was significantly smaller in inflamed (18.8%) and non-inflamed (15.8%) areas of UC. The proportions of neurones containing ChAT and SP were significantly higher in inflamed (11.8%) and non-inflamed (13.9%) areas than in controls (5.0%).

CONCLUSION

Remodelling of myenteric neurones in UC involves a shift from mainly cholinergic to more SP positive innervation. This effect may constitute part of the neuronal basis for the motility disturbances observed in UC.

Percutaneous ethanol injection vs. resection in patients with small single hepatocellular carcinoma: a retrospective case-control study with cost analysis

BACKGROUND

Percutaneous ethanol injection and hepatic resection are the most widely used curative therapeutic options for patients with compensated liver disease and small hepatocellular carcinoma.

AIM

To compare percutaneous ethanol injection and hepatic resection in a selected group of consecutive French patients with a single hepatocellular carcinoma, smaller than or equal to 50 mm, in terms of survival, recurrence rate of malignancy and direct costs.

METHODS

The analysis of two contemporary cohorts of Child-Pugh A or B patients with a single hepatocellular carcinoma of < or = 50 mm treated by percutaneous ethanol injection (n=55) or hepatic resection (n=50).

RESULTS

Long-term survival was not significantly different between the two groups when the size of hepatocellular carcinoma was less than 30 mm. However, the survival of patients with hepatocellular carcinoma larger than 30 mm was higher after hepatic resection than after percutaneous ethanol injection (P=0.044). The cumulative direct costs were significantly higher in patients treated by hepatic resection than in those treated by percutaneous ethanol injection regardless of the tumour size. The calculated costs per month of survival in patients treated with percutaneous ethanol injection and hepatic resection were 999 vs. 3865 euros, respectively (P < 0.001).

CONCLUSIONS

Percutaneous ethanol injection is more cost effective than hepatic resection in patients with a single hepatocellular carcinoma smaller than 30 mm. However, in patients with a larger tumour, long-term survival is higher after hepatic resection.

Vasoactive intestinal peptide is involved in the inhibitory effect of interleukin-1 beta on the jejunal contractile response induced by acetylcholine

Although previous studies have shown that interleukin-1 beta (IL-1 beta) decreases acetylcholine (ACh)-induced intestinal contraction by an action on the enteric nervous system, the neuromediator(s) involved are still unknown.

AIM

To determine the role of nitric oxide (NO), vasoactive intestinal peptide (VIP) and/or adenosine triphosphate (ATP) in mediating this inhibitory effect.

METHODS

The effects of NO synthase inhibitors, VIP and ATP antagonists on motor response to the ACh were investigated before and after 90-min exposure of a rat preparation of jejunal longitudinal muscle-myenteric plexus to IL-1 beta. NG-nitro-L-arginine methyl ester, NG-nitro-L-arginine and NG-monomethyl-L-arginine were used to inhibit NO synthase, VIP (10-28) and [D-p-Cl-Phe6, Leu17] VIP to block VIP receptors, and suramin to block ATP receptors.

RESULTS

NO synthase inhibitors failed to block the inhibitory effect of IL-1 beta on ACh-contracted jejunum smooth muscle. Suramin also failed to affect IL-1 beta-induced inhibition, whereas VIP antagonists abolished it. Moreover, the action of IL-1 beta was partly reproduced by VIP.

CONCLUSIONS

While neither NO nor ATP accounts for the inhibitory effect of IL-1 beta on ACh-contracted jejunum, VIP seems to be a key-mediator of this effect.

Decreasing oesophageal acid exposure in patients with GERD: a comparison of rabeprazole and omeprazole

BACKGROUND

Rabeprazole has been shown to be more potent and faster than other proton pump inhibitors in in vitro studies and highly effective in decreasing oesophageal acid exposure in patients with gastro-oesophageal reflux disease (GERD).

AIM

This study was a multicentre, double-blind, placebo-controlled, randomized, parallel-group comparison of three active treatment regimens utilizing two different proton pump inhibitors, or placebo, administered over 7 days in patients with GERD.

METHODS

Eighty-two patients with symptomatic GERD were given placebo, rabeprazole 10 mg b.d., rabeprazole 20 mg o.m., or omeprazole 20 mg o.m. for 7 days. Twenty-four hour oesophageal pH monitoring was performed at baseline and repeated at the conclusion of the treatment period.

RESULTS

At the end of study, the percentage time (mean +/- s.d.) with pH < 4 over a 24-h period was significantly decreased by the three active regimens but without significant difference between them (9.27 +/- 4.77; 2.53 +/- 4.27; 2.02 +/- 1.71 and 2.91 +/- 4.06 for placebo, rabeprazole 10 mg b.d., rabeprazole 20 mg o.m. and omeprazole 20 mg o.m., respectively). Acid exposure was normalized in 90% of patients treated with rabeprazole 10 mg b.d., 95% treated with rabeprazole 20 mg o.m., 78% treated with omeprazole 20 mg o.m., and only 9.5% of patients treated with placebo. Both rabeprazole and omeprazole were well-tolerated.

CONCLUSIONS

Although rabeprazole 20 mg o.m. showed greater activity numerically, this study demonstrates that rabeprazole 10 mg b.d. and 20 mg o.m. are equivalent to omeprazole 20 mg o.m. in decreasing oesophageal acid exposure.

Review article: managing the dyspeptic patient--an interactive discussion

Dyspepsia, a common disorder, can present some difficult clinical dilemmas. Physicians should explore some of the more challenging cases of dyspepsia in a setting that fosters interactive dialogue among colleagues, as was the case at the interactive discussion reported below. A panel of experts presented and discussed three case histories. The audience was able to choose from among several options for diagnosis or treatment and recorded their votes by means of an electronic handset. The first case concerned the relationship between continued non-steroidal anti-inflammatory drug (NSAID) use and recurrent upper gastrointestinal (GI) symptoms without ulcer or Helicobacter pylori infection. The second was a woman with complex upper GI symptoms including heartburn. The last featured a young man with dyspepsia and no alarm symptoms. The first case showed that a standard dose of proton pump inhibitor (PPI) is the best treatment for patients with gastritis who continue to use NSAIDs. The second case revealed that 24-h pH monitoring can be used to establish a relationship between symptoms and reflux episodes. The third case demonstrated that it can be difficult to make a definitive diagnosis based on clinical symptoms, and that patients with endoscopy-negative reflux disease usually respond well to PPI therapy.

Projections of excitatory and inhibitory motor neurones to the circular and longitudinal muscle of the guinea pig colon

The aim of this study was to identify myenteric pathways to the circular and longitudinal muscle of the guinea pig proximal colon. To identify excitatory and inhibitory muscle motoneurones, we applied the neuronal retrograde tracer DiI onto the circular or longitudinal muscle layer and performed additional immunohistochemistry for nitric oxide synthase (NOS) and choline acetyltransferase (ChAT). On average 166 +/- 81 circular muscle motoneurones (CMMN) and 100 +/- 74 longitudinal muscle motoneurones (LMMN) were labelled by DiI tracing. Myenteric pathways innervating the muscle were either ascending (DiI-labelled neurones with oral projections) or descending (DiI-labelled neurones with anal projections). The circular muscle was preferentially innervated by ascending pathways (66.0 +/- 9.1%). Most ascending CMMN were ChAT-positive (87.2 +/- 8.5%), whereas descending CMMN were mainly NOS-positive (82.3 +/- 14.6%). Most ascending (62.2 +/- 11.1%) and descending (82.0 +/- 12.5%) CMMN had circumferential projection preferences (circumferential projections were longer than projections along the longitudinal gut axis). In contrast to the polarised projections to the circular muscle, the longitudinal muscle was equally innervated by ascending (46.2 +/- 15.1%) and descending (53.9 +/- 15.1%) neurones. Ascending and descending pathways to the longitudinal muscle consisted predominantly of ChAT-positive neurones (98.1 +/- 1.9% and 68.0 +/- 8.5%, respectively), and both pathways had prominent longitudinal projection preferences. Only 25.5% of the descending LMMN were NOS-positive. In conclusion, the circular muscle in the proximal colon is innervated by descending inhibitory (NOS-positive neurones) and ascending excitatory (ChAT-positive neurones) pathways. In contrast, the longitudinal muscle is primarily innervated by ascending and descending excitatory motoneurones, and only a small proportion of the descending pathway consisted of inhibitory motoneurones.

H. pylori and transient lower esophageal sphincter relaxations induced by gastric distension in healthy humans

The role of Helicobacter pylori infection in the control of lower esophageal sphincter (LES) motility, especially the occurrence of transient LES relaxations (TLESRs), was studied in eight H. pylori-positive and eight H. pylori-negative healthy subjects. During endoscopy, biopsy specimens were taken from the cardia, fundus, and antrum for determinations of H. pylori status, gastritis, and proinflammatory cytokine mucosal concentrations. LES motility was monitored during three different 30-min periods: baseline, gastric distension (barostat), and gastric distension with CCK infusion. Gastric distension significantly increased the TLESR rate, whereas CCK increased the rate of distension-induced TLESRs further and reduced resting LES pressure without significant differences between infected and noninfected subjects. H. pylori status did not influence resting LES pressure or gastric compliance. Cytokine mucosal concentrations were increased in infected patients, but no correlation was found with the TLESR rate, which was also independent of inflammation at the cardia, fundus, and antrum. These results suggest that H. pylori-associated inflammation does not affect the motor events involved in the pathogenesis of gastroesophageal reflux.

Interleukin-8 increases acetylcholine response of rat intestinal segments

BACKGROUND

Interleukin-8 (IL-8) is a pro-inflammatory cytokine highly expressed in inflammatory bowel diseases, but whose effects on intestinal motility are unknown.

AIM

To characterize the role of IL-8 in the contraction of rat intestinal segments.

METHODS

Contractile response to acetylcholine (ACh 10-6 M) in terminal ileal segments (including mucosa) from Wistar rats was measured before and after incubation (15, 30, 60 or 90 min) with IL-8 (1 ng/mL), and after 60 min of incubation with different doses of IL-8 (0, 0.1, 0.5, 1, 10 and 100 ng/mL). The effects of blocking neural transmission with tetrodotoxin (TTX) and inhibiting protein synthesis (cycloheximide) were tested. The contractile response of longitudinal muscle-myenteric plexus preparations (i.e. without mucosa) was measured after 60 min of incubation with 0.1 and 1 ng/mL of IL-8.

RESULTS

IL-8 increased ileal contraction induced by ACh 10(-6) M. This augmentation was significant after 60 min of incubation (58%, P=0.01) and persisted after 90 min (18%, P=0.04). A 60-min incubation period showed a dose-related effect, beginning at 0.5 ng/mL (30%, P=0.003) and reaching a peak at 1 ng/mL (58%, P=0.01). The same effect was also observed on colonic segments. TTX did not affect the IL-8 increase of ACh-induced contractions, which was completely abolished by cycloheximide. IL-8 had no significant effect on longitudinal muscle-myenteric plexus preparations.

CONCLUSION

In vitro, IL-8 increases contractile response of the ileum to ACh in a dose-dependent manner. This effect is not neurally mediated, but seems to involve protein synthesis by intestinal mucosa.

Proinflammatory role of leptin in experimental colitis in rats benefit of cholecystokinin-B antagonist and beta3-agonist

Leptin, a hormone primarily secreted from adipocytes, plays a key role in controlling body weight homeostasis. In vitro studies indicate that it is also implicated in immune responses. Hyperleptinaemia has been reported in acute inflammation, especially during the early stages of intestinal inflammation in rats. The present study investigated the possible role of leptin in the pathogenesis of trinitrobenzene sulfonic acid (TNBS)-induced colitis in rats. Since no specific antagonist of leptin is available, a CCK-B antagonist (YM022) and a beta3 agonist (BRL37344) were used in this study to inhibit leptin secretion. Colitis was induced by intracolonic instillation of TNBS in rats. Five TNBS-groups were subcutaneously implanted with micropumps containing: placebo, YM022, BRL37344, BRL37344 and exogenous leptin simultaneously, or leptin alone. At sacrifices, colitis severity was assessed by macroscopic and histological scoring systems and by determination of tissue myeloperoxidase activity. The TNBS-induced hyperleptinaemia was significantly reduced by YM022 and BRL37344 (p<0.05). Inhibition of leptin secretion markedly reduced colonic inflammation, whatever the criteria considered (i.e. macroscopic, histological or biochemical). In contrast, administration of exogenous leptin completely abolished the beneficial effect of leptin-lowering drugs on colitis severity. These results provide the first direct evidence for an important deleterious role of leptin in the pathogenesis of experimental intestinal inflammation and suggest that a pro-inflammatory activity is attributable to leptin in vivo. Further studies are required to determine if these results have clinical significance.

Endoscopy-negative reflux disease

Endoscopy-negative reflux disease (ENRD) is more prevalent than reflux esophagitis, especially in a primary care setting. Acid-sensitive esophagus (ie, reflux-related symptoms with normal acid exposure at 24-hour pH monitoring) is part of the gastroesophageal reflux disease spectrum. ENRD is not a mild disease (symptoms return frequently and have an impact on quality of life), but it rarely progresses to the erosive stage. In patients with atypical or extra-esophageal manifestations, pH monitoring remains useful, and symptom analysis (symptom index or symptom-associated probability) is of pivotal importance. A proton pump inhibitor (PPI) test may represent a cost-effective alternative to 24-hour pH monitoring. However, well-designed validation studies are necessary to assess the diagnostic value of PPI tests and improve specificity without reducing sensitivity. Management of ENRD is based on the same principles as that of reflux esophagitis. Restoration of quality of life is the major goal. Proton pump inhibitors are not more (and are sometimes even less) effective in non-erosive reflux disease than in reflux esophagitis. Different long-term strategies (continuous maintenance, intermittent or on-demand therapy) are available, depending on the needs of the patient. Antireflux surgery may be indicated in carefully selected patients. In the future, pharmacologic approaches targeted to transient lower esophageal sphincter relaxation or visceral perception should be developed.

[Acid-sensitive esophagus: natural history and effect on the quality of life. Comparison with gastroesophageal reflux]

The acid hypersensitive esophagus (AHE) is characterized by a normal esophageal acid exposure but a significant association between symptoms and reflux episodes. The natural history of AHE remains poorly known. We therefore conducted a follow-up study to compare the initial presentation and natural history of AHE and classical GERD. Quality of life (QOL) was also assessed.

PATIENTS AND METHODS

Two groups of patients referred to our laboratory for 24-hour pH-monitoring (between 1991 and 1996) were compared. Group 1 consisted of 127 consecutive patients with AHE. Group 2 consisted of 101 patients with GERD. All patients were invited by mail to fill-in two questionnaires, the first concerning clinical course and therapeutic needs and the second QOL (questionnaire Reflux-Qual). Finally 62% and 59% of group 1 and 2 respectively did respond to both questionnaires. The corresponding follow-up periods were 4.1 and 4.3 years, respectively.

RESULTS

The two groups did not differ at initial presentation with regard to age, sex, symptoms prevalence and severity of esophagitis (80% of group 1 and 75% of group 2 were endoscopy-negative patients). At an average follow-up of 4 years symptoms persisted in 80% and 71% of patients respectively. Seventy five per cent of patients in both groups continued to take antireflux drugs. QOL scores were similarly reduced in both groups (71 +/- 26 vs 70 +/- 27).

CONCLUSIONS

The initial presentation and clinical outcome of AHE and GERD are similar. QOL is notably impaired and the majority of patients continue to receive antireflux medications.

Butyrate inhibits inflammatory responses through NFkappaB inhibition: implications for Crohn's disease

BACKGROUND/AIM

Proinflammatory cytokines are key factors in the pathogenesis of Crohn's disease (CD). Activation of nuclear factor kappa B (NFkappaB), which is involved in their gene transcription, is increased in the intestinal mucosa of CD patients. As butyrate enemas may be beneficial in treating colonic inflammation, we investigated if butyrate promotes this effect by acting on proinflammatory cytokine expression.

METHODS

Intestinal biopsy specimens, isolated lamina propria cells (LPMC), and peripheral blood mononuclear cells (PBMC) were cultured with or without butyrate for assessment of secretion of tumour necrosis factor (TNF) and mRNA levels. NFkappaB p65 activation was determined by immunofluorescence and gene reporter experiments. Levels of NFkappaB inhibitory protein (IkappaBalpha) were analysed by western blotting. The in vivo efficacy of butyrate was assessed in rats with trinitrobenzene sulphonic acid (TNBS) induced colitis.

RESULTS

Butyrate decreased TNF production and proinflammatory cytokine mRNA expression by intestinal biopsies and LPMC from CD patients. Butyrate abolished lipopolysaccharide (LPS) induced expression of cytokines by PBMC and transmigration of NFkappaB from the cytoplasm to the nucleus. LPS induced NFkappaB transcriptional activity was decreased by butyrate while IkappaBalpha levels were stable. Butyrate treatment also improved TNBS induced colitis.

CONCLUSIONS

Butyrate decreases proinflammatory cytokine expression via inhibition of NFkappaB activation and IkappaBalpha degradation. These anti-inflammatory properties provide a rationale for assessing butyrate in the treatment of CD.

Relationships between transit time in man and in vitro fermentation of dietary fiber by fecal bacteria

OBJECTIVE

To assess the effects of drug-induced changes in mean transit time (MTT) on the activity of human fecal flora in vitro.

METHODS

The activity of fecal flora was estimated by the ability of a fecal inoculum to ferment a substrate (beet fiber) in vitro in a batch system for 24 h. The inoculum was collected from 8 healthy volunteers studied during three 3-week randomized periods, who received a controlled diet alone (control period) or the same diet with either cisapride or loperamide. Cisapride and loperamide were adjusted in order to halve and double MTT measured during the control period. At the end of each period, the percentage disappearance of the initial added substrate and the concentration and the profile of short-chain fatty acids (SCFAs), were determined.

RESULTS

In the control period, the pH of the inoculum and SCFA concentration were inversely related to MTT (P=0.0001). Individual SCFA production was also significantly related to MTT (P<0.01). Cisapride-reduced transit time was associated with a significant rise in the concentrations of total SCFAs (P<0.05), propionic and butyric acids (P<0.05) and the percentage substrate disappearance (P<0.05). Inverse relations were observed during the loperamide period. Moreover, MTT was inversely related to the percentage substrate disappearance (P<0.001), SCFA production (P<0.001) and butyrate production (P<0.0005).

CONCLUSION

Changes in MTT alter bacterial activity and modify the bacterial pathways affecting the proportion of individual SCFAs. European Journal of Clinical Nutrition (2000) 54, 603-609

Short-chain fatty acids induce cytoskeletal and extracellular protein modifications associated with modulation of proliferation on primary culture of rat intestinal smooth muscle cells

Short-chain fatty acids are the main end products of bacterial fermentation of carbohydrates. Their role on the metabolism and biology of colonocytes is now well characterized. However, the functional consequences of their presence on intestinal smooth muscle cells remain poorly studied. We aimed to assess the effect of different short-chain fatty acids on ileal and colonic smooth muscle cells in primary culture and on A7R5 line. Butyrate (above 0.1 mM) inhibited A7R5 cell proliferation, while at low concentration (0.05 to 0.5 mM) butyrate significantly stimulated the proliferation of ileal and colonic myocytes in primary culture. An inhibition was observed at higher concentrations. Collagenous and noncollagenous protein synthesis was stimulated by butyrate. Moreover, butyrate stimulated actin and myosin expression. Thus, butyrate, which is produced by dietary fiber fermentation, may affect intestinal muscles by directly acting at the molecular level on myocytes.

How do we offer clinical relief to patients with gastro-oesophageal reflux disease?

In gastro-oesophageal reflux disease (GORD), the majority of patients are endoscopy negative. However, symptoms can affect the quality of life irrespective of the presence of oesophagitis. Proton pump inhibitors (PPIs) are far more effective than H2 receptor antagonists (H2RAs) or prokinetics with regard to the speed of symptom relief. Despite this undisputed progress, there is some conflict on whether symptoms should be managed until full resolution in endoscopy-negative patients or in those with mild oesophagitis. Considering that GORD is not a life-threatening condition, some authorities admit that patients should accept minimal residual symptoms. They argue that PPIs are expensive while healthcare resources are limited, and that long-term safety of PPIs has not been completely established. Moreover, they underline that many patients do not seek medical help and are satisfied with self-medication (with antacids/alginates or even over-the-counter H2RAs). On the other hand, some clinicians prefer a full resolution of symptom strategy because this is now achievable with modern PPIs without serious concerns in terms of tolerance and safety. Indeed, quality of life is rapidly restored by PPIs. Moreover, symptom relief by PPIs is highly predictive of healing, making endoscopic control unnecessary at least for mild/moderate oesophagitis. Finally, there is also some controversy over whether we should start treatment with PPIs or use less potent drugs as first-line therapy. If one considers not only the direct cost of drugs, but also the indirect ones (e.g. sick leave days), it is reasonable to think that PPIs may be more cost-effective than H2RAs or prokinetics, at least when the disease is of moderate or severe intensity. In conclusion, with modern PPIs like lansoprazole, rapid and full resolution of symptoms is now achievable in the large majority of patients.

Isosorbide mononitrate and propranolol compared with propranolol alone for the prevention of variceal rebleeding

The aim of this study was to test the effectiveness of isosorbide-5-mononitrate (IM) as an adjunct to propranolol (PR) in the prevention of variceal rebleeding. Ninety-five cirrhotic patients with variceal bleeding were randomly assigned to treatment with PR + IM (46 patients) or PR alone (49 patients). Eighteen patients in the PR + IM group and 28 in the PR group had rebleeding during the 2 years after randomization. The actuarial probability of rebleeding 2 years after randomization was lower in the PR + IM group (40.4% vs. 57.4%) but the difference was not significant (P =. 09). However, the decrease in the risk of rebleeding reached statistical significance after stratification according to age, i.e. less than 50 versus >/=50 years old, (P =.03) or by adding an additional year of follow-up (P =.05). No significant difference was found in rebleeding index and survival. The multivariate Cox analysis indicated first, that both treatment (P =.03) and age (P =. 001) were factors predictive of rebleeding and second, that PR + MI reduced the risk of rebleeding by half (relative risk: 0.51, 95% confidence interval: 0.28-0.95). Seven patients in the PR + MI group and 1 patient in the PR group had to discontinue one of the drugs because of adverse events (P =.03). These results suggest that the addition of IM improves the efficacy of PR alone in the prevention of variceal rebleeding in cirrhotic patients. However no beneficial effects were observed on other parameters reflecting the efficacy of treatment.

Does the route of feeding modify gastric emptying in rats?

BACKGROUND

It has been shown that the pattern of previous nutrient intake can influence gastric emptying. However, the effect of the absence of enteral stimulation in the setting of a normal energy supply on gastric emptying has not been examined. The aim of this study was to determine whether the absence of enteral stimulation during total parenteral nutrition (TPN) could modify gastric emptying in rats.

METHODS

Two experiments were performed. First, gastric emptying of a peptone meal was compared between rats receiving TPN, oral liquid diet (same solution as TPN), or regular diet (control group) for 10 days. In the second experiment, gastric emptying of two test meals (40% peptone and 25% glucose) was studied before and after rats received TPN or intragastric nutrition (same solution as TPN) for 10 to 12 days.

RESULTS

In experiment 1, gastric emptying of 40% peptone in the TPN and liquid diet groups was slower than that in the control group. This difference was significant between the TPN group and the control group (p < .01) but not between the liquid diet and control groups (p = .076). Gastric emptying of this meal in the TPN and liquid diet groups was similar. In experiment 2, no difference in gastric emptying of 40% peptone or 25% glucose was found between rats receiving TPN and those receiving intragastric nutrition for 10 to 12 days.

CONCLUSIONS

The composition of diet not the route of feeding is important in the modification of gastric emptying by the pattern of previous nutrient intake.

Modulation by colonic fermentation of LES function in humans

Colonic fermentation of carbohydrate has been shown to influence gastric and intestinal motility. Our aim was to investigate the effects of colonic infusion of lactose and short-chain fatty acids (SCFAs) on lower esophageal sphincter (LES) function in humans. LES pressure (LESP), transient relaxations of LES (TLESRs), and esophageal pH were monitored over 6 h on 4 different days in 7 healthy volunteers. After 1 h of baseline recording, the effects of different colonic infusions (270 ml of isotonic or hypertonic saline, 30 g lactose, or 135 mmol SCFAs) were tested in fasting conditions and after a standard meal. Peptide YY (PYY) and oxyntomodulin (OLI) were also measured in plasma. Both lactose and SCFA infusions increased the number of TLESRs as well as the proportion of TLESRs associated with acid reflux episodes, but saline solutions did not. The postprandial fall of LESP was enhanced by previous SCFA infusion. Plasma PYY and OLI increased similarly after all colonic infusions. Colonic fermentation of lactose markedly affected LES function, and this effect was reproduced by SCFA infusion. Whether the mechanisms of this feedback phenomenon are of hormonal nature, neural nature, or both remains to be determined.

Butyrate and trichostatin A effects on the proliferation/differentiation of human intestinal epithelial cells: induction of cyclin D3 and p21 expression

BACKGROUND

Sodium butyrate, a product of colonic bacterial fermentation, is able to inhibit cell proliferation and to stimulate cell differentiation of colonic epithelial cell lines. It has been proposed that these cellular effects could be linked to its ability to cause hyperacetylation of histone through the inhibition of histone deacetylase.

AIM

To analyse the molecular mechanisms of butyrate action on cell proliferation/differentiation and to compare them with those of trichostatin A, a well known inhibitor of histone deacetylase.

METHODS

HT-29 cells were grown in the absence or presence of butyrate or trichostatin A. Cell proliferation and cell cycle distribution were studied after DNA staining by crystal violet and propidium iodide respectively. Cell cycle regulatory proteins were studied by western blot and reverse transcription-polymerase chain reaction. Cell differentiation was followed by measuring brush border enzyme activities. Histone acetylation was studied by acid/urea/Triton acrylamide gel electrophoresis.

RESULTS

Butyrate blocked cells mainly in the G(1) phase of the cell cycle, whereas trichostatin A was inhibitory in both G(1) and G(2) phases. Butyrate inhibited the mRNA expression of cyclin D1 without affecting its protein expression and stimulated the protein expression of cyclin D3 without affecting its mRNA expression. Trichostatin A showed similar effects on cyclin D1 and D3. Butyrate and trichostatin A stimulated p21 expression both at the mRNA and protein levels, whereas their effects on the expression of cyclin dependent kinases were slightly different. Moreover, butyrate strongly stimulated the activity of alkaline phosphatase and dipeptidyl peptidase IV, whereas trichostatin A had no effect. Finally, a six hour exposure to butyrate or trichostatin A induced histone H4 hyperacetylation. At 15 and 24 hours, histone H4 remained hyperacetylated in the presence of butyrate, whereas it returned to control levels in the presence of trichostatin A.

CONCLUSIONS

The data may explain how butyrate acts on cell proliferation/differentiation, and they show that trichostatin A does not reproduce every effect of butyrate, mainly because of its shorter half life.

Pathways and receptors involved in peptide YY induced contraction of rat proximal colonic muscle in vitro

BACKGROUND

Peptide YY (PYY) is involved in the regulation of several gut functions, including secretion and motility. It exerts its effects through a family of six receptors, commonly named the Y receptor family.

AIMS

To characterise the effects of PYY on strips of rat proximal colon in vitro, and to determine the pathways and receptors involved.

METHODS

Contractions of strips removed from the muscle layer of rat proximal colon were recorded under isometric conditions, using PYY, Y receptor agonists and antagonists, and nerve blockers. Reverse transcription-polymerase chain reaction was also performed to detect the presence of mRNA coding for Y receptors. Finally, smooth muscle cells were isolated to estimate the cell length and intracellular Ca(2+) concentration in the presence and absence of PYY.

RESULTS

PYY, neuropeptide Y (NPY), pancreatic polypeptide (PP) and [Leu31,Pro34]NPY induced a dose dependent contraction of strips from proximal colon. Tetrodotoxin partially inhibited the PYY and NPY induced contractions, and strongly inhibited the PP induced contraction. Specific antagonists showed the involvement of cholinergic nicotinic receptors and NK1 receptor. BIBP 3226, a specific Y1 antagonist, did not modify the colonic smooth muscle response to PYY, whereas blocking L-type Ca(2+) channels with D-600 abolished its effects. Moreover, PYY induced an increase in intracellular Ca(2+) concentration, associated with a reduction in cell length. mRNA encoding Y1 and Y4 receptors were detected in the muscle strips.

CONCLUSIONS

These findings suggest that PYY stimulates colonic contractile activity in vitro through (a) a nervous Y4 dependent pathway and (b) a pathway involving a potential new receptor on myocytes.